ESTIMATING CUTTING TIME AND COST WITH DIFFERENT TOOL MATERIALS

A 9-in (22.86-cm) diameter steel shaft is to be heavy roughed with either of two cutting tools high-speed steel (HSS), or cemented carbide. The work material is AISI 1050 having a hardness of 200 BHN. Feed rate is 0.125 in/r (3.17 mm/r); depth of cut = 1.0 in (25.4 mm); tool life is based on 0.030-in (0.726-mm) flank wear. Choose the most effective tool to use if the tool signature is: ?6, 10, 6, 6, 15, 15, 1/16 R; the tool-changing time = 4 min for both tools; the cost of a sharp tool = $0.50 for HSS and $2.00 for cemented carbide; and M = machine labor plus overhead rate, $/min = 15 cents for each type of tool.

Calculation Procedure:

1. Determine the minimum-cost tool life for each type of tool material

Analyses of the economics metal of cutting with different types of cutting-tool materials are often plotted on two bases Figs. 1 and 2. Figure 1 shows the machining cost, tool cost, and nonproductive cost added to show the total cost per piece. In Fig. 2, the machine time, tool-changing time, and nonproductive time are added and plotted as the total time per piece.

Figure 1: Total cost per piece is found by adding the plots of machining costs, tool costs, and nonproductive costs. ( T. E. Hayes and American Machinist.)

Figure 2: Total time per piece is found by adding the...